package eu.siacs.conversations.utils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Random;

import android.os.Bundle;
import android.util.Log;

public class DNSHelper {
	public static Bundle getSRVRecord(String host) throws IOException {
		InetAddress ip = InetAddress.getByName("8.8.8.8");
		try {
			Class<?> SystemProperties = Class.forName("android.os.SystemProperties");
			Method method = SystemProperties.getMethod("get", new Class[] { String.class });
			ArrayList<String> servers = new ArrayList<String>();
			for (String name : new String[] { "net.dns1", "net.dns2", "net.dns3", "net.dns4", }) {
			    String value = (String) method.invoke(null, name);
			    
				if (value != null && !"".equals(value) && !servers.contains(value))
			    	ip = InetAddress.getByName(value);
			        servers.add(value);
			        Bundle result = queryDNS(host, ip);
			        if (!result.containsKey("error")) {
			        	return result;
			        }
			}
		} catch (ClassNotFoundException e) {
			ip = InetAddress.getByName("8.8.8.8");
		} catch (NoSuchMethodException e) {
			ip = InetAddress.getByName("8.8.8.8");
		} catch (IllegalAccessException e) {
			ip = InetAddress.getByName("8.8.8.8");
		} catch (IllegalArgumentException e) {
			ip = InetAddress.getByName("8.8.8.8");
		} catch (InvocationTargetException e) {
			ip = InetAddress.getByName("8.8.8.8");
		}
		return queryDNS(host, ip);
	}
	
	public static Bundle queryDNS(String host, InetAddress dnsServer) {
		Bundle namePort = new Bundle();
		try {
		Log.d("xmppService","using dns server: "+dnsServer.toString()+" to look up "+host);
		String[] hostParts = host.split("\\.");
		byte[] transId = new byte[2];
		Random random = new Random();
		random.nextBytes(transId);
		byte[] header = { 0x01, 0x20, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
				0x00, 0x01, 0x0c, 0x5f, 0x78, 0x6d, 0x70, 0x70, 0x2d, 0x63,
				0x6c, 0x69, 0x65, 0x6e, 0x74, 0x04, 0x5f, 0x74, 0x63, 0x70 };
		byte[] rest = { 0x00, 0x00, 0x21, 0x00, 0x01, 0x00, 0x00, 0x29,
				0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
		ByteArrayOutputStream output = new ByteArrayOutputStream();
		output.write(transId);
		output.write(header);
		for (int i = 0; i < hostParts.length; ++i) {
			char[] tmpChars = hostParts[i].toCharArray();
			byte[] tmp = new byte[tmpChars.length];
			for (int j = 0; j < tmpChars.length; ++j) {
				tmp[j] = (byte) tmpChars[j];
			}
			output.write(tmp.length);
			output.write(tmp);
		}
		output.write(rest);
		byte[] sendPaket = output.toByteArray();
		int realLenght = sendPaket.length - 11;
		DatagramPacket packet = new DatagramPacket(sendPaket,
				sendPaket.length, dnsServer, 53);
		DatagramSocket datagramSocket = new DatagramSocket();
		datagramSocket.send(packet);
		byte[] receiveData = new byte[1024];

		DatagramPacket receivePacket = new DatagramPacket(receiveData,
				receiveData.length);
		datagramSocket.setSoTimeout(3000);
		datagramSocket.receive(receivePacket);
		if (receiveData[3]!=-128) {
			namePort.putString("error", "nosrv");
			return namePort;
		}
		namePort.putInt("port",calcPort(receiveData[realLenght + 16],
						receiveData[realLenght + 17]));
		int i = realLenght + 18;
		int wordLenght = 0;
		StringBuilder builder = new StringBuilder();
		while (receiveData[i] != 0) {
			if (wordLenght > 0) {
				builder.append((char) receiveData[i]);
				--wordLenght;
			} else {
				wordLenght = receiveData[i];
				builder.append(".");
			}
			++i;
		}
		builder.replace(0, 1, "");
		byte type = receiveData[i+1];
		if (type!=-64) {
			namePort.putString("error", "nosrv");
			return namePort;
		}
		namePort.putString("name",builder.toString());
		return namePort;
		} catch (IOException e) {
			Log.d("xmppService","io execpiton during dns");
			namePort.putString("error", "nosrv");
			return namePort;
		}
	}

	static int calcPort(byte hb, byte lb) {
		int port = ((int) hb << 8) | ((int) lb & 0xFF);
		if (port>=0) {
			return port;
		} else {
			return 65536 + port;
		}
	}
	
	final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();
	public static String bytesToHex(byte[] bytes) {
	    char[] hexChars = new char[bytes.length * 2];
	    for ( int j = 0; j < bytes.length; j++ ) {
	        int v = bytes[j] & 0xFF;
	        hexChars[j * 2] = hexArray[v >>> 4];
	        hexChars[j * 2 + 1] = hexArray[v & 0x0F];
	    }
	    return new String(hexChars);
	}
}